Aircraft passenger cabins are known to have lighting fixtures designed to illuminate a specific targeted area, such as for reading, sometimes referred to as “task” lighting. Aircraft passenger cabins also are known to have lighting fixtures that direct light along the surfaces of walls and ceilings, sometimes referred to as “general” or “wash” lighting. The illumination pattern produced by the wash lighting is considered to have an effect on the mood and well-being of the passengers.
Traditionally, hidden fluorescent lamps have been used for providing wash lighting, such as along the ceiling of an aircraft passenger cabin. These fluorescent lamps provide a wide variation in surface brightness that may not be ideal for the comfort of the passengers. In addition, the light provided by fluorescent lamps tends to be artificial-looking. It is also known to use fixtures with light emitting diodes (LEDs) as a supplement or replacement for fluorescent lamps to provide wash lighting. However, in this case, although LEDs may provide an illumination pattern in which color changes over time, the pattern of the light remains static.
Digital projectors can be used to provide motion patterns in the cabin illumination, but such projectors are large, expensive and consume a great deal of power. Lower cost and lower power devices exist for producing moving projected patterns, but such devices typically operate by projecting a light source through a lens which is mechanically moved to simulate motion in the projected image. There are at least two drawbacks with this approach. First, the range of mechanical motion is small, so that the image has a pattern that is quickly repeated and does not provide the beneficial effects of motion which is random or pseudo-random. Second, the use of motors or other drive devices in multiple lighting devices mounted in an aircraft is costly and inevitably will lead to failures over time due to the numerous moving parts required.
Accordingly, there is a need for a low cost illumination device for producing illumination patterns simulating natural motion which also eliminates the need for moving parts used to generate such illumination patterns.